Development History:http://i.imgur.com/FeUUh87.jpg
(Standard Swiss military issue STGW.90 assault rifle)
The PE90 was Switzerland's attempt to adopt a modern small caliber assault rifle, which was both lighter and less expensive than the P57. I am not sure exactly how well they succeded there, but the result definitely was one of the finest assault rifles ever devised.

In 1978, the Swiss military decided to look into the possibility of adopting a small caliber, select-fire rifle to replace the full power and fullsized P57 battle rifle. The new design had to be accurate out to at least 300 meters, less expensive to manufacture, lighter, more compact, and more modular than the older design. Two versions were called for; a standard full length rifle for the infantry, and a so-called 'Headquaters' carbine for use in special situations.

http://i.imgur.com/gquPdah.jpg
(SIG SG540 Prototype rifle)
Schweizerische Industrie-Gesellschaft Neuhausen (SIG) had already been working on a .223/5.56mm caliber assault rifle for some time by this point. In the 1960s, it released the SG530-1 prototype, which had both a gas piston and roller delayed bolt. Next, the SG540 came out. It kept the gas piston and switched to an AK47 style rotating bolt with 2 large locking lugs. It featured an adjustable gas system, HK style drum diopter sights, fixed polymer buttstock, and lightweight bipod. Later, a version would be offered with a folding stock made from tubular steel. To allow it to be both easier and cheaper to mass produce, it was built with more stamped metal parts and even some made from investment castings. The SG540 actually went into limited production, with the French firm of Manurhin purchasing a manufacturing license. The French military bought several thousand of these domestically produced SG540s, using them as stop-gap rifles until the FAMAS bullpup was fully operational. Additionally, Beretta used it as the basis for its own AR70 assault rifle, which was eventually adopted in a modified form by the Italian military as the AR70/90.

http://i.imgur.com/1OamZug.jpg
(SIG SG543 trials carbine)
In 1979, SIG submitted its latest assault rifle model for military trials. Actually, it submitted two versions. The SG541 had a rifle length barrel and gas system, and the SG543 was a compact carbine. The SIG design competed against the C42 submitted by Waffenfabrik Bern. It officially was selected for further development in 1983. At the same time, the 5.6mm GP90 cartridge was chosen as Switzerland's new service round. GP90 is very similar to 5.56mm NATO but just different enough not to be the same. It has a bullet weight of 63g, rather than the original American 55g or later NATO 62g.

Originally, both the new rifle and cartridge were to go into service immediately; however, manufacturing complications and budget cuts drastically extended the process. In 1984, the SG541 received several design improvements and was redesignated as the SG550. The gas system was improved and made more corrosion resistant and a new pattern of skeletonized polymer stock was introduced. Also, a four way fire mode selector was made standard: safe, single, 3 rd burst, and full-auto. These changes were carried over to the SG543 too, and it became the SG551. Finally in 1986, the Swiss military took delivery of the first batch of the new rifles, which were officially designated as Sturmgewehr Model of 1990. It would take over a decade for the entire military to be so re-equipped though.

The PE90 features typical Swiss quality and attention to detail. While definitely less time consuming and resource intensive to build than SiG's previous P57, it is still one of the most expensive 5.56mm caliber military rifles in the world. Tuned for optimal performance in the often fridgid Swiss Alps, it is highly reliable and durable. The SG550 has a long-stroke gas piston system and AK47 style rotating bolt. Despite this, it is quite accurate, especially at close to medium ranges. The standard rifle has a 20.8" long barrel, with intrigal flash hider and grenade ring. The inside of the flash hider is threaded to accept a blank firing device also. The gas system is adjustable with two settings, and under the gas block there is a P57 style bayonet lug. The light aluminium alloy bipod is attached to the long polymer handguard, and fits into grooves on its underside when not in use. The upper and lower receivers are made from stamped and welded steel, and the barrel screws into a machined front trunion. The charging handle is very similar to the AK47's but is rubber coated and upswept. It does reciprocate with the bolt, and rides inside a channel protected by a rubber dustcover. The mag release is virtually the same as the one on the P57, as are the takedown pins. The fire mode selector is ambidextrous, and much better placed than on the P57. There is an automatic last-round bolt hold open device, and external release lever. The trigger is quite light and smooth, and it is adjustable too. The trigger guard is made of stamped steel and can be folded up to either side, to reach the trigger if wearing thick gloves. The pistol grip is made of ribbed polymer and has a small storage compartment inside. The buttstock has an inner frame made of steel, with an outer shell of polymer and a ridged rubber buttplate. It easily folds to the right side and locks into a tab on the side of the handguard. Most Swiss military PE90s have dark green furniture, but many of the other variants come in black.
The P90 has HK style diopter sights, with a windage adjustable hooded front blade; and an elevation and windage adjustable rear drum with 3 apertures and a notch. Night sights are standard on all models, with a fold up front blade and two rear points as part of the drum's notch setting. Unlike the P57's sights, the ones on the PE90 do not fold, however they have a much lower profile. This also means they are much closer to the bore's axis. The firearm feeds from translucent polymer magazines, which have tabs on the side to lock multiple units together. The standard mag holds 20 rounds, and an extended 30 round version is available for special situations.

The PE90 disassembles easily and without the need for tools. Just open the upper and lower receivers by removing the rear takedown pin, then press down on the release lever and pull out the charging handle. The bolt group will fall out the back of the upper receiver. Rotate the bolt to separate it from the carrier. To remove the gas system, press the spring loaded detent and rotate the gas valve until it pulls out. Then the gas piston and recoil spring assembly falls out the front of the gas tube. If you want to remove the tube itself for a cleaning, just press the detent again and rotate the end of the tube until it too pulls free of the gas block. If you want to completely separate the upper and lower receivers, just remove the front takedown pin and there you go. All in pieces. At this point the handguards will easily come off too, as they are held on by the lower receiver. The buttstock is attached with a single long pivit pin, which can be knocked out with a punch and light hammer, but this isn't neccessary for cleaning.

http://i.imgur.com/055grDx.jpg
(SG55x Family Photo)
The standard rifle goes by several names and designations: STGW.90, PE90, P90, SG550, Fusil d'assaut 90, or more simply FASS90. Originally designed and manufactured by SIG, it has been built and sold under the Swiss Arms Neuhausen (SAN) brand name since 2000, when SiG sold its firearms division to the Lu¨ke & Ortmeier Group. Many versions and variants in the SG55x family exist today.

The SG550-1 is the STGW.90 designed for the 5.6mm 63g GP90 cartridge with a 1 in 10 twist rate. The SG550-2 on the otherhand is meant to fire the standard 62g 5.56mm NATO round and has a 1 in 7 twist rate. There is a DMR variant of the rifle called the 550-1 Sniper, with scope, 25.8" accurized barrel, fully adjustable trigger, adjustable stock, cheak rest, and more ergonomic and adjustable pistol grip; which are all standard features from the factory.

The carbine version is designated as the SG551 and has a 14.3" barrel, shortened gas system and handguards, no bayonet lug, and can not fire rifle grenades. The military designation for this version seems to be STGW.90k. It is in limited use with a few Swiss units such as the Infantry Grenadiers and the Para Recon Company. It too is made in -1 and -2 variants. The 'SWAT' carbine variant is designed for use in humid or wet environments, with a more corrosion resistant finish to many of its internal parts. The SG551 LB has an extended 17.9" barrel, which allows it to fire rifle grenades and mount a bayonet.

The SG552 is out of production now, but was an even shorter submachinegun sized version. It has sometimes been referred to as the SiG Commando by some users and in some promo material. It had a 8.9" barrel, fixed post style charging handle, removable flash hider, and redesigned recoil system with the spring in the back as in an AK47. Its handguards were made by manually cutting down the standard set used on the SG550, and then drilling 5 vent holes in each side to provide for additional cooling. Today, it has been replaced by the SG553, which has the same short barrel with muzzle threading, gas tube, and handguards; but uses a shortened SG550 recoil system and standard removable charging handle. Also it has a thinner gas piston than the standard 550/551, which is fluted to save on weight. Several different types of flash hider have been offered for this variant, including the original 4 prong, an updated 3 prong, and a Rotex suppressor compatable device. Both SMG sized firearms have been offered in a LB version, with a longer 13.6" barrel. The SG553 seems to only be offered in an all black colour scheme. The Swiss military adopted a limited number of the SG552-1 LB as the STGW.04, and later the SG553-1 LB as the STGW.04/07. They have been used by specialized type units such as paratroopers.

Modern SG55x versions are offered either with fixed diopter sights or with a weaver rail and folding backup iron sights. They can be had with the original pattern stamped steel lower, or one manufactured from machined aluminium. A 'NATO' version is offered, which feeds from all standard AR15/M16 type magazines. Quadrail handguards are an option, as is a stock which both folds and has an adjustable length of pull. A variant of the subcompact known as the SG553R is even available chambered for the 7.62x39mm (M43) Russian cartridge. Finally, most models are offered as a semi-auto only, with the 'SP' suffix added to the designation. For example, the SG550-2SP was the most popular civilian legal variant imported into the USA during the 1980s. A special carbine variant with an extended 16.1" barrel was very briefly exported to the USA in the late 1980s, designated as the SG551-2SP. Other SG551-2SPs though, such as those sold in Europe and to American law enforcement, had standard 14.3" carbine barrels.

The SG550-1 is still the standard issue rifle of the Swiss military today. It also uses many SG551-1 carbines and a few SG552/3-1 LB subcompacts when the need arrises. Law enforcement uses the series too, especially the SG551 carbine and the standard short barreled SG552 SMG. Adding up all versions and variants, it is estimated that over 600,000 SG55x firearms have been built in Switzerland to date, with production still on going. 450,000 STGW.90 assault rifles were delivered to the Swiss military, while 35,000 civilian SG550 rifles have been sold within and outside of Switzerland.

The pattern has undergone very few changes since its introduction in 1986. Nevertheless, a few design tweeks have been introduced such as a slightly larger magazine well. Also, the furniture was redesigned in the early 1990s. The buttstock's mold lines became less pronounced, the underside was reshaped, the sling loop was moved to the centerline, and the buttplate lost much of its concave curviture. Finally, the vent holes in the handguard were reshaped. I've also heard tell that the shade of OD Green used was slightly changed.

The STGW.90 has proven itself a fine standard issue firearm in the Swiss military. It is highly reliable and durable, and plenty accurate for its class. It is easy to clean and maintain. This is a heavy rifle to be firing a small diameter bullet, but the flip side is that it has low felt recoil and is very controllable in full-auto. The barrel makes it a bit long by modern standards, but at least it has an excellent folding stock. Some dislike its ergonomics, mostly the placement of its safety selector and rock & lock magazines. The mags themselves are top notch though. They are very lightweight, durable, and easy to load by hand. They have survived many torture tests, including being frozen and dropped from a height while fully loaded. The one part of the rifle that does seem substandard is the light bipod, which is frankly rather useless and likes to fold on its own. One also should not forget that this firearm hasn't really been put through intensive, real world combat, as has the AK47, FN FAL, M16, HK G3, Steyr AUG, or many others. Still, the STGW.90 is a good fit for Switzerland.

Semi-Auto SG55x's in the USA:
Preban Swiss made SG550s bring at least $8,000 in the USA today, with most going for closer to $10,000. As for preban SG551s? since so few were brought in, they go for even more, say approximately $12,000-$15,000. This is why the American SIG556 and SIG551-A1 clones look so damn attractive to most people in the market for something like an STGW.90. Afterall, they use the same internal parts, even if they are US, rather than Swiss made. The differences are mostly external: furniture, barrel profile, sights, etc.

Back in the 1980s, between 450 and 500 SG550 rifles came into the country. Most were the SG550-2SP with its 1in7 twist rate, though a few SG550-1SPs did come over with the original 1in10 twist. In addition to those, 45-50 SG551-2SP carbines with 16.2" barrels made it in before the 1989 ban. A tiny number of the 550-1 Sniper rifle variant was imported too. Finally, an unknown number of semi-automatic PE90s slipt in, many without import marks. These rifles were the same as the SG550-1SP, except they had both the grenade tention ring and bayonet lug. I've seen estimates for these rifles from 10 to 50 here in the USA. I tend to feel it is towards the higher end, since they seem to come up for sale rather frequently. Prices for these range from $10,000 to $15,000, depending on condition and accessories. Some like them for their authenticity, while others question the legality of how they were brought into the USA and if they are truely preban? Also, many seem to show more wear and tear than standard SG550-2s, which is a bit unusual.

This rifle has an interesting history, and there are reasons why I obtained it so 'aforedably.' Sometime in its past, someone decided it would be a great idea to drill and tap the receiver for a scope base. Normally, this is the deathnail for any military type firearm, but with so few SG550-1SPs in the USA it was worth restoring. In addition to that, the same idiot drilled 2 holes in the buttstock to attach a cheak riser, which he 'made' from an HK93 forearm. Long story short, someone back-when nearly destroyed a beautiful and rare rifle. I found this rifle online but was in the middle of buying a house, so I couldn't afored it at the time. I convinced a friend and gunsmith to buy it instead. He did and repaired the receiver and stock....the receiver I challenge anyone to figure out it was ever molested! As for the stock, well there is only so much you can do with polymers. Still, I now have an authentic SG550-1SP for nearly half of what they usually go for. Recently, he decided he didn't need it and i was able to snap it up. Plus, since hey its not mint in the box or anything, no harm in taking it to the range!

I purchased this Swiss SG551-2SP SWAT two years ago, when a batch of police surplus carbines were available from Michael's Machines (i.e. MM or Mike Otte). It cost about half of what a preban would have, and it has an original length 14.3" barrel, with internal threading for a blank device. Best of all it is exempt from 922(r), so it is all Swiss. Luckily, I had a buyer for a couple of high end firearms I was hoping to move at the time, so I was able to swing it....just. I am glad I did though. Only about 110 were sold, and since its already surplus, I don't feel bad about firing it. I see no reason to have such a fine rifle and not be able to shoot and enjoy it. It really completes my Swiss military issue firearms collection.

This is one of the 200 SG553Ps imported by M+M (Colorado Gun Sales), with 100 of the diopter version and 100 of the railed type. The very first guns had a non-threaded and heavy 10" barrel, but this was soon changed to a standard weight 8.9" one with 1/2x28" threading. It was reported that these early pistols had a 1 in 10 twist rate, but more recently evidence has come to light which suggests all were actually 1 in 7. Later, SIG Arms (SIG USA) fucked everything up for everyone by importing more, with a horrible marking and a $1k lower price point. I had this one for several months. It was very well made and shot nicely, but in the end I decided to pass it along. Honestly, I am glad I did after what SIG Arms pulled. The SG553P is the same as the military SG553-2, except for being in semi-auto only and having no buttstock. Also, it has the current machined lower and all black finish.

When SIG took over the importation of the 553P line from M+M, it had to double mark the first batch of pistols for some reason. Maybe the original M+M markings had already been ingraved and SIG had no choice but to add a second set to make the ATF happy? Either way, most people barely tolerate a single import marking and two was far too many for some. However, later SIG imported 553Ps like mine here have only a single marking. They are the same as the earlier M+M guns, except for the flash hider. The M+M had a Swiss style birdcage, where as the SIG has a 552/3 style 3 prong. Honestly, I like the 3 prong as it is more distinctive. Fit and finish is still excellent, and for under $3,000, I just couldn't say no to getting another one to complete my collection. Oh and they are a shit load of fun to shoot too.

USA Made Copies:
Back in 2004-2005, rumours abounded of SIG opening an American production facility for the SG55x series of rifles. To put it bluntly, they didn't just let us down, they fucked us over. Originally, we were given the SIG556ER in 2007, which had a heavy plastic 'fish gill' handguard, an aluminium rail bolted on top of the receiver, took standard AR15 mags, and had a fixed M4 telescoping buttstock. The very first ones were built with some Swiss parts; but soon, USA subcontractors were used instead. Then the SIG556 Commando came out with a side folding Magpul stock, which was better but still very Americanized. Later still, the SIG556 Classic was released, which still took AR15 mags but at least had a Swiss style folding buttstock (which was not Swiss made). The P556 pistol was orignally supposed to have a 8.9" barrel and use the same length of gas system as the SG553. However, when SIG USA ran into reliability problems, it lengthened everything by about an inch; making the barrel 10" and meaning no 553 gas system parts would be compatable. Finally, the SIG551-A1 was released, which was in SAN (Swiss) grey, took Swiss magazines, and had an authentic Swiss side folding buttstock. Don't worry though, having a good thing with the -A1, SIG Arms then switched the original Swiss stock with a foreign made copy without telling anyone. SIG made a factory SBR by mating the 551-A1's lower with a P556 upper too. In the end, they canceled the SIG556 and SIG551-A1 lines altogether and replaced them with the new SIG556XI line. For the XI line's "improvements" just use Sir. Google.

The SIG556 and SIG551-A1 were parts compatable copies of the original SG551, however the SIG556XI is its own bastardized variant.

Originally, I bought a SIG556 Classic, and while it was a good enough rifle, it just wasn't Swiss enough. When the SIG551-A1 came out, i was quite happy with it, and I set about modifying mine to be more like an original SG551LB. I installed a bayonet lug, Swiss style flash hider, original Swiss handguards, and Swiss diopter sights. It was quite a good clone, but I found I had nearly $2,500 in it after everything. Then I found Mike Otte and his SG551-2SP police trade-ins. I was able to sell my SIG551-A1 for $3,000 and sold 2 other guns to free up the additional $2,200 that I needed for the trade-in rifle.

I was happy to have an all original and Swiss firearm, but still deep in my heart wanted an STGW.90 type rifle. I considered getting another SIG551-A1 and rebarreling it, but by 2013-2014, original PE90 parts were getting very expensive. It would have taken a whole new barrel, new gas system, new handguards, and new diopter sights. I could have also put on an original Swiss lower too. The project would have cost me over $5,000 if i were to do it right, so I just shelved the whole idea. I checked Gunbroker from time to time, looking for a preban SG550, but prices were always well out of reach for me. I even considered selling my SG551 too but hated the idea of letting go of a legit milspec carbine.

So with building one out and prebans looking out of range for my budget, I was getting used to the fact that I would never own a SG550 type rifle. Then the right one for me came along. I hate that bubba got ahold of it back-when; but on the otherhand, his modifications were what allowed it to fall into my price range. Originally, the seller (an FFL out in Nevada), listed it on Gunbroker at $7,500.00. It had no takers, because most collectors able to afored it at that price, could afored to spend a bit more and get an unmodified example. So the dealer dropped it to $7,000 and then $6,000; and still no takers. After chatting with him a couple times and learning the extent of bubba's modifications, i offered him $4,000. I wasn't trying to screw him, but I was afraid both the receiver and stock might be write-offs, so i was offering him about what a SG550-1 parts kit might go for. After some time, he came back with a price of $5,000 and finally one of $4,500. I turned it over to my friend and gunsmith, who after a bit of debate and worry, took the guy up on his offer.
The seller obviously did not know anything about SG55x rifles, nor apparently about safe packing techniques. When my friend received the box, the mag was just kicking around loose in there and the charging handle was sticking out of the side. In fact, the handle was destroyed, as during shipping all of the rubber had been ground off it.

So my friend had 3 things to do. He had to weld up the holes in the top of the receiver, fill in the 2 holes on the top of the buttstock, and find a new charging handle. Best guess as to why someone did something like this to a preban SG550? Probably some young kid inherited it from an old relative or friend. Then having little money (and no brains), he modified it into a 'sniper' rifle in his garage, using whatever parts he had laying around. My friend is a great welder and managed to basically make the holes in the receiver disappear. He even found the right shade of Swiss grey to make the repaired areas match the rest of the metal. Next, he had to fill in the holes in the stock, and again he got lucky and found the right colour to dye the plastic filler with. Finally, he bought a NOS charging handle from a friend of his in...Switzerland or Britan? I can't recall which one right now.
At anyrate, when he was done, the rifle looked infinitely better and was nearly perfect. Also good news in that it appears bubba shot it very little. It looks to have had only a couple mags put through it honestly, so the bore and gas system are very clean. There are few marks behind the ejection port too from brass cases.

Buying this rifle was a gamble since we really didn't know the extent to which it had been abused; in the end though, it worked out just fine.

As to why i decided to get another SG553P, well, prices have fallen and I always did think it was a nifty firearm. When I had just it and the 551, it seemed a bit silly to have both the carbine forms but not the original rifle. However, once I got the 550 rifle I'd always wanted, i started to feel it would be great to have all of the major variants. If down the road I was forced to part with one to free up some money, I could still have the long rifle and shorty SMG carbine as opposite ends of the range. That's just kind of how my mind works. I like compare and contrast like that. That said, often I do feel the 551 carbine in the middle is just right. It is much shorter and lighter than the 550, yet still has more range and utility than the tiny 553.

Well there you have my revised and expanded SG55x Thread. I've dug around alot and learned as much as I could without being able to actually look at posted pictures. I am sure I got some things wrong, but I hope the broad strokes are right. I really love these guns and the whole SIG/SAN series. If you asked me why, I would have a difficult time explaining. Objectively I know the SG55x has faults and flaws, but at the same time I really enjoy shooting it and it just has a mystique for me.